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Method and apparatus for locating underground cast iron pipe joints

  • US 7,466,134 B2
  • Filed: 08/04/2006
  • Issued: 12/16/2008
  • Est. Priority Date: 08/04/2006
  • Status: Active Grant
First Claim
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1. A method for locating underground cast iron pipe joints comprising the steps of:

  • determining the location and orientation of an underground cast iron pipe;

    passing an oscillating electrical current through an electrically driven resonant coil disposed substantially vertically above said underground cast iron pipe, forming an oscillating magnetic field;

    inducing an electrical current in each of two resonant sensor coils disposed within said oscillating magnetic field;

    measuring a magnetic reluctance between said electrically driven resonant coil and each of said resonant sensor coils, producing an initial magnetic reluctance; and

    measuring said magnetic reluctance while moving said coils above and parallel to said cast iron pipe, whereby measured magnetic reluctances substantially different from said initial magnetic reluctance constitutes proximity to a cast iron pipe joint.

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